<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>原生的事件绑定</title>
</head>

<body>
  <button id="btn1">按钮1</button>
  <button id="btn2">按钮2</button>
  <button onclick="demo()">按钮3</button>
  <script>
    const btn1 = document.getElementById('btn1')
    btn1.addEventListener('click', () => {
      alert('按钮1被点击了')
    })

    const btn2 = document.getElementById('btn2')
    btn2.onclick = () => {
      alert('按钮2被点击了')
    }

    function demo() {
      alert('按钮3被点击了')
    }
  </script>
</body>

</html>